Fuel

Gasoline Octane Rating
All vehicles except Cobra are designed to use regular unleaded fuel with an octane rating of 87. At service stations, the octane rating is displayed in a label on the pumps.
- In some regions, regular grade fuels are sold with octane ratings of 86 or lower. This is common in areas of high altitude.
- It is not recommended to use such fuels.
- Always use a fuel with an octane rating of 87, even if it is sold as a midgrade or premium.
- Using a fuel with a lower octane rating can cause persistent and heavy knocking, which can damage the engine.
- Do not be concerned if the engine sometimes knocks lightly when driving up a hill or when accelerating. See a dealer or a qualified service technician if, when using a fuel with the specified octane rating:

-- the engine knocks heavily under all driving conditions
-- the engine knocks lightly while being driven at cruising speed on level roads.

In most cases, it should not be necessary to use a premium grade of fuel with an octane rating of higher than 87.

If the engine has difficulty starting, rough engine idle or hesitation when the engine is cold, it may be caused by fuel with low volatility.
- Trying a different grade or brand of fuel may solve the condition. If the condition persists, see your dealer or a qualified service technician.

The Mustang Cobra engine has been designed to operate using PREMIUM UNLEADED fuel with an octane rating of 91 or higher.
- Regular unleaded fuel with an octane rating of 87 may be used if necessary.
- For optimum performance and driveability, it is recommended that premium unleaded fuel be used.

In some regions, premium grade fuels are sold with octane ratings of less than 91.
- This is common in areas of high altitude.
- It is recommended that only those premium fuels with an octane rating of 91 or higher are used.

Always use a fuel with an intake system deposit control detergent that helps keep the vehicle's intake valves clean.